Many industrial devices utilize a water supply, which is evaporated for the purposes of heating, cooling, power generation and the like. All untreated water supplied contain quantities of multivalent metallic salts, especially those based on calcium and magnesium. In the process of evaporating the water, the salts become concentrated to a point to where they precipitate out of solution in the form of a scale, i.e., an insoluble, crusty coating throughout the functional parts of the apparatus. The formation of scale is generally undesirable because the scale is a poor conductor of heat and may otherwise interfere with the efficiency of the apparatus. Removal of scale also usually requires shut-down of the apparatus to enable mechanical and/or chemical cleaning. Also, in general, it would be desirable to provide a method and apparatus for causing selective disposition of solutes which are at or near saturation point in a solution.